Process of coating iron with aluminium.



S. UYENL).

PROCESS OF COATING IRON WITH ALUMINIUM.

APPLICATION FILED IUNE4, 1912.

11,165,92Q Patented Dec. 28, 1915.

By W- H/S ATTORNEY IN FACT.

SADAMASA UYENO, OF TOKYO, JAPAN.

PROCESS OF COATING IRON WITH ALUMINIUM.

Specification of Letters Patent.

Patented Dec. 28, 11915.

Application filed June 4, 1912. Serial No. 701,542.

T 0 all whom, it may concern Be it known that I, SADAMASA UYENO, a subject of the Emperor of Japan, residing at No. 127 Hakusan-Goten-Machi, Koishikawa-Ku, Tokyo, Japan, have invented new and useful Processes of Coating Iron with Aluminium, of which the following is a spec-,

ification.

This invention has for its object to provide an improved process for coating iron sheets, rods, wires or other iron articles with aluminium. Iron coated with aluminium is particularly useful for a variety of industrial purposes as it is thereby rendered free from oxidation.

It has heretofore been proposed to coat iron with aluminium by immersing it into molten aluminium and while immersed, rubhing its surface vigorously; but to carry out this process, the aluminium must be heated high enough to form an alloy directly with iron on the surface thereof. However aluminium heated to such a high temperature easily attacks the substance of iron too deep, with the result that the process cannot be applied for practical purposes. It has also been proposed to coat iron with aluminium by simply dipping it into molten aluminium heated to a comparatively low temperature. Further, it has been proposed to coat iron with aluminium by first coating it with tin or zinc, then dipping this into molten aluminium; but by this means only an alloy of aluminium and tin or zinc is formed which adheres to the surface of iron.

With the improved process of my invention aluminium is caused to adhere direct to the surface of the iron in a perfect manner so that it will not come off or tarnish or corrode under the action of air, water or heat or be stripped off by mechanical action because my improved process enables the metal to be directly covered with a layer of pure aluminium in place of the zinc or tin alloy hereinabove described.

According to my invention the iron articles to be coated with aluminium are first tinned or galvanized, that is to say, are coated with tin or zinc in any well known manner and they are then immersed in one or successively in two or more vessels containing molten aluminium and while so immersed the surfaces of the articles are swept by steel brushes. The articles are finally pressed or rolled to give them a smooth surface and may in addition if desired be subected to a polishing process to give them luster.

Iron, tin and zinc are metals which readily form alloys with aluminium, in fact iron alloys with aluminium more readily than it does with either tin or zinc. My invention is based on the fact that when iron coated with tin or zinc is immersed in a vessel containing molten aluminium and its surface is swept by means of a steel brush or other equivalent device, the tin or zinc is entirely set free from the surface of the iron combining with the surrounding aluminium to form an alloy. while the aluminium adheres to the iron surface in its place thus entirely replacing the tin or zinc.

The apparatus used in carrying the pres ent invention into effect comprises a number of suitable vessels or melting pans arranged in a series upon a fire grate. These vessels contain molten aluminium and are provided with suitable steel brushes which are used to sweep the faces of the articles to be coated with aluminium.

The process comprises the following stages: 1. A piece of iron plate, for example is first tinned or galvanized in the usual way, care being taken not to leave any oxid between the plate and the coating. 2. The iron plate thus coated with tin or zinc is next immersed in the first of a series of vessels containing molten aluminium where it is swept with a steel brush. It is then passed into the second vessel undergoing a similar treatment and if necessary into the remaining vessels in succession being subjected to the sweeping operation in each. 3. After being removed from the last vessel the plate is passed between suitable rollers by which it is pressed and rolled to give it a smooth surface. 4, If desired the plate may be passed through a suitable polishing or burnishing machine to give it luster.

A suitable apparatus which may be employed for coating the plates with aluminium is illustrated in the accompanying drawings, in which- Figure 1 illustrates an apparatus for coating iron sheets. Fig. 2 is an end view, showing a ladle which may be used for transferring the molten aluminium from one vessel to the other, Fig. 3 being a side view of the same. Fig. 4 is an end view showing an apparatus for dipping iron sheets in the molten vessels and Fig. 5 is a side view of the same.

Referring now to Fig. 1, the apparatus therein shown is intended to be used for coating a continuous iron sheet. 1 indicates a furnace of any suitable construction and 2, 3, 4 are melting pans for holding the molten aluminium. Said pans may be provided with outlets 5, 6, 7 having suitable cocks for removing the molten aluminium when desired. 8, 9, 10, 11, 12 and 13 indicate fixed steel brushes between which the iron sheet, as shown by the dotted line, is passed in the direction of the arrows. The sheet is drawn through the pans by means of a pair of rolls 14.

For transferring the molten aluminium from one vessel to the other, the arrangement shown in Figs. 2 and 3 may be employed. 15, 16 are. pairs of rails located above the melting pans forming a run-way carrying wheels or rollers 17 by which the hook 18 is guided through a sleeve 18. This hook is suspended by a chain 19, and carries a ladle 20 of any suitable form which can be lowered into the melting pans by means of the chain and when full may be readily moved from one pan to the next as desired; A somewhat similar device is shown in Figs. 4c and 5 for plunging separate sheets of iron into the melting pan. The run-way is formed by rails 15, 16 as before, which support a carriage running on rollers 17, the hook 18 in this instance, being arranged to support the iron sheet indicated at 21 which is to be treated. The steel brushes indicated at 22 in Fig. 5 are arranged so that the iron sheets 20 can be passed vertically between them and so as to be swept by the brushes as they ascend and descend into the melting pans indicated at 23.

Any suitable apparatus can of course be utilized for carrying out my improved process, the apparatus above described being shown merely by way of example.

For coating wires, rods or pipes, similar apparatus to that above described may be employed and for articles which have only small surface irregularities the same arrangement may be employed within the limits of the elasticity of the steel brushes. For articles which are more irregular in form special arrangements will be required to enable the brushes to penetrate to every part, the essential feature being that the whole surface which it is desired to coat with aluminium shall be swept by the brush.

The temperature of the molten aluminium used in the coating process is about 700 to 800 degrees centigrade which is somewhat higher than the melting point of the metal. In the first vessel, however, Where at least the surface of the immersed article has to acquire a temperature above the melting point of aluminium, the temperature of the molten bath will be maintained somewhat higher than that given above otherwise the article must be kept in the bath for a longer time until it acquires the desired temperature. Obviously the temperature will depend upon the quantity of the aluminium and the mass or size of the article to be coated. The articles are passed direct from one vessel to the next, the number of vessels being dependent upon the kind of article being coated and also whether a lustrous finish is ultimately required. It will be understood that the important thing is that every part of the surface shall be swept with the brushes so that the aluminium will be caused to alloy with the tin or zinc and the surface of the iron coated with aluminium. In the first vessel the greater part of the tin or zinc will be replaced but as there will still be some remaining it is necessary to pass the articles through two, three or more vessels until all the tin or zinc is eliminated and only pure aluminium is left on the surface of the iron. With articles which are easily swept by the brushes, the replacement will take place more quickly and fewer vessels will therefore be required but with articles of irregular shape the sweeping is rather difficult and must be repeated many times before the replacement of the tin or zinc is complete, consequently a greater number of vessels will be required than in other cases.

If the aluminium coating is not very pure it will lose its luster somewhat with the lapse of time, but with a pure coating this does not occur, consequently where the article is not required to take a high polish a less number of vessels may be used.

The time during which the article is immersed in each vessel depends mainly upon its shape and will be sufiiciently long to enable a proper sweeping to be effected, but since in the first vessel, generally the surface of the article to be treated has to attain the temperature of the melting point of aluminium in order to make the process effective, it will be desirable to lengthen the time of immersion in this vessel unless the article is heated by some suitable device to the proper temperature before it is immersed.

The rolling process is desirable where the shape of the articles will permit, as it gives a smooth surface but in the case of irregularly shaped articles some equivalent process, for example by polish balls, may be employed, this stage of the processvnot constituting a part of the present invention.

The aluminium in the baths will gradually become alloyed with zinc or tin as the case may be but owing to the small thickness of the coating it will be some time before the bath is rendered useless from this cause.

The bulk of the tin or zinc will be found in the first bath, therefore this bath will require purification before the remaining ones in the series.

A plate treated by my improved process will be found to have the aluminium coating so closely adherent that it will not undergo any changes under ordinary conditions. Iron plates coated by my process with aluminium prove more serviceable than ordinary tinned or galvanized iron plates and when used for the manufacture of domestic utensils or for building purposes they give a better appearance and surpass other metals in durability.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. The process of coating iron with aluminium which comprises coating the iron with tin and brushing the surface while the same is immersed in molten aluminium.

2. The process of coating iron plate with aluminium which comprises tinning the plate, immersing the same in molten aluminium, brushing same while so immersed and passing the same between rollers to give it a smooth surface.

3. The process of coating iron with aluminium which comprises coating iron with a suitable metal and entirely replacing such metal by aluminium.

4. The process of coating iron with aluminium which comprises coating the iron with tin and entirely replacing the tin by aluminium.

5. The process of coating iron with aluminium which comprises coating the iron with a suitable metal, immersing the same in molten aluminium and sweeping the surface with a metal brush while so immersed.

Dated this first day of September, 1911.

SADAMASA UYENO. Witnesses:

GENJI KURJBARA, HARUTADE YASUMURA. 

